This disclosure relates generally to the field of digital imaging. More particularly, but not by way of limitation, it relates to techniques for registering multiple images for high dynamic range imaging using motion sensor data.
Traditional photography and digital imaging take pictures of a scene at a single exposure level in the imaging device, resulting in an image with a limited contrast range. The limited contrast (or dynamic) range results in a loss of detail in bright areas of a picture if the imaging device used one exposure setting, and a loss of detail in dark areas if the imaging device used a different exposure settings. Typical image sensors do not have the dynamic range to capture the image as the human eye would see it. A common example of the effect is a photograph where the sky appears almost white, while objects on the ground are exposed sufficiently to allow seeing details of those objects.
High Dynamic Range (HDR) photography is a set of methods used in digital imaging to allow a greater dynamic range between the lightest and darkest areas of an imaging that would be possible using standard imaging techniques. This wide dynamic range allows HDR images to represent more accurately the range of intensity levels found in real scenes. Although there are multiple ways of creating HDR images, the most common technique combines images taken with different exposure settings.
Some imaging devices now allow capturing an HDR image by automatically capturing a sequence of three or more standard dynamic range images and performing HDR techniques to create an HDR image from the standard dynamic range images. The imaging device typically captures a sequence of differently exposed images of the same subject matter, each at one exposure level. The images are registered to each other, and various techniques such as tone mapping, are applied to merge a registered HDR image with better or exaggerated local contrast for artistic effect. The most common technique for registering the images is to match their visual features using software or firmware built into the camera or other imaging device. However, software registration techniques based on visual feature mapping require significant computational resources.